Method for operating an oil supply and controller

ABSTRACT

A method is provided for operating an oil supply for a combustion engine and/or a transmission system of a motor vehicle particularly with start/stop-automatic, comprises the steps, that a deceleration of the motor vehicle is detected, at least one status parameter, which correlates with the manner of the deceleration, is monitored, a future oil pressure of the oil supply is estimated based on the status parameter and the actual oil supply control strategy, and if the estimated future oil pressure is below a predetermined threshold of the oil pressure, an oil pump for filling an accumulator tank of the oil supply is activated. Since the accumulator tank is filled in advance of a possible automatic stop a sufficient high oil pressure, when the combustion engine is started again, is safeguarded, wherein the period of time for accomplishing the automatic stop is not lengthened. This leads to a reduction of the fuel consumption and the CO 2 -emissions of the combustion engine without dealing with a too low oil pressure at the start of the combustion engine.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to British Patent Application No. 0914479.1, filed Aug. 19, 2009, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The technical field relates to a method for operating an oil supply for a combustion engine and/or a transmission system of a motor vehicle as well as a corresponding controller, by means of which the oil pressure of the oil supply system can be controlled.

BACKGROUND

From DE 100 41 789 A1 it is known to override the command for an automatic stop of a combustion engine with start/stop-automatic at low oil pressure, so that an oil pump can fill an accumulator tank first before the combustion engine is stopped due to the present automatic stop command. Due to the override a sufficient oil pressure can be provided, when the combustion engine starts.

It is a disadvantage of such kind of a method that the fuel consumption and the CO₂-emissions of the combustion engine are high.

It is at least one object to provide a method for operating an oil supply as well as a controller, by means of which the fuel consumption and the CO₂-emissions of the combustion engine can be reduced without dealing with a too low oil pressure at the start of the combustion engine. In addition, other objects, desirable features, and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.

SUMMARY

The method according to an embodiment of the invention for operating an oil supply for a combustion engine and/or a transmission system of a motor vehicle particularly with start/stop-automatic comprises the steps, that a deceleration of the motor vehicle is detected, at least one status parameter, which correlates with the manner of the deceleration, is monitored, a future oil pressure of the oil supply is estimated based on the status parameter and the actual oil supply control strategy, and if the estimated future oil pressure is below a predetermined threshold of the oil pressure an oil pump for filling an accumulator tank of the oil supply is activated.

The method according to an embodiment of the invention provides the possibility to fill the accumulator tank not only when an automatic stop of the combustion engine is initiated by the start/stop-automatic but even before all conditions for initiating the automatic stop are met. The future oil pressure is particularly calculated for a point in time, when the automatic stop of the combustion engine due to the start/stop-automatic is scheduled based on the development and/or the actual value of the status parameter(s). For that purpose the development of the status parameter(s) can be extrapolated. Due to the correlation of the status parameter(s) to the manner of the deceleration, at least a rough estimation of the development of the speed of the motor vehicle and thus the deceleration or vice versa can be calculated. For that purpose even rather qualitative parameters are sufficient, wherein specific measured values of different parameters are preferred. Since the accumulator tank is filled in advance of a possible automatic stop a sufficient high oil pressure, when the combustion engine is started again, is safeguarded, wherein the period of time for accomplishing the automatic stop is not lengthened. The period of time until the automatic stop is initiated after a stop of the motor vehicle can even be shortened. This leads to a reduction of the fuel consumption and the CO₂-emissions of the combustion engine without dealing with a too low oil pressure at the start of the combustion engine.

This result is realized by turning away from the actual oil supply control strategy for a short period of time for filling the accumulator tank in addition to the actual oil supply control strategy. The decision to change the actual oil supply control strategy can be based on a very low number of monitored values like amount of the deceleration and/or amount of the vehicle speed, this means the speed of the motor vehicle, without significant problems. Further it is used the insight that the automatic stop will only occur after a deceleration and not after an acceleration of the motor vehicle. Thus, it is possible to trigger the start of the method, when specific conditions particularly with respect to the amount of the deceleration and/or the vehicle speed are met. For instance the method is initiated when the speed of the motor vehicle is below a particularly amount, like 20 km/h and the amount of deceleration is above zero, that means a negative acceleration of the motor vehicle is present. Particularly the status parameters can be provided via a CAN-bus, so that additional sensors are not necessary. In the case that a stop of the combustion engine did not occur as estimated no drawbacks are present. The regular standard oil supply control strategy can deal with the filled accumulator tank without problems.

The predetermined threshold of the oil pressure is particularly chosen such that, when the combustion engine starts, an operation of the oil pump is not necessary for a particular period of time. Particularly the accumulator tank is filled for providing an oil pressure significantly above the threshold for providing a safety reserve and/or considering an increasing deceleration over the period of time until the stop of the motor vehicle as calculated prior. The required oil pressure for this period of time can be provided by the level of oil in the accumulator tank only. For starting the combustion engine an automotive battery does not have to provide electric energy to the oil pump during the engine crank event. The respective electric energy is saved for starting the combustion engine. After the start of the combustion engine the necessary electric energy can be provided by an electric generator driven by the combustion engine. The charge of the automotive battery can be saved. The method can be applied to conventional pure combustion engine motor vehicles, when the automatic stop of the start/stop-automatic is used for stopping the combustion engine automatically at a stop of the motor vehicle with zero vehicle speed. The method can be further applied to a hybrid motor vehicle, when the automatic stop of the start/stop-automatic is used for changing from combustion engine mode to electric machine mode.

Particularly the status parameter is the amount of the deceleration, the speed of the motor vehicle or the brake status, whether the brakes are applied. Preferably more than one status parameter is used. For instance the brake status may be a signal for starting the method according to invention and/or the combination of the amount of the vehicle speed and the amount of the deceleration may be used for calculating a point of time in the future, when the motor vehicle may stop.

In a preferred embodiment based on the development and/or the actual value of the at least one status parameter, particularly speed of the motor vehicle and amount of the deceleration, a stop-time is calculated, until which the speed of the motor vehicle will be zero and/or an automatic stop of the combustion engine due to the start/stop-automatic will occur, and the future oil pressure is calculated for the end of the stop-time. The stop-time t_(stop) can be calculated by the ratio of the amount of the actual vehicle speed v and the amount of the actual deceleration a (t_(stop)=v/a), wherein the actual deceleration can be determined by the development of the vehicle speed (a={dot over (ν)}), with {dot over (ν)}=dv/dt). Particularly an additional period of time is added for safety. The additional period can be a percentage p of the calculated stop-time by means of the ratio v/a, wherein 1%≦p≦25%, particularly 2%≦p≦20%, preferably 3%≦p≦15% and most preferred 5%≦p≦10% can be given. In the case that the start/stop-automatic provides a minimum delay until the automatic stop is initiated after the stop of the motor vehicle, this delay is usually a sufficient safety time, so that the stop-time can be calculated with respect to the calculated point of time, when the motor vehicle stops without an additional period of time for safety purposes. In the case that the intended delay of the start/stop-automatic is long compared to the maximum filling time of the accumulator tank, the stop-time can be calculated with respect to the calculated point of time, when the automatic stop of the combustion engine due to the start/stop-automatic will occur. In this case it is preferred to consider an additional period of time for determining the stop-time for being on the safe side with respect to the intended minimum oil pressure of the oil supply system.

Preferably, the oil pump is activated if the automatic stop of the start/stop-automatic is unblocked, wherein the automatic stop is particularly blocked, when the charge of an automotive battery is below a predetermined value, a temperature and/or other value of a vehicle component is out of a predetermined range and/or a combustion engine control is on override mode from a subsystem particularly from transmission control or air conditioning control. It is considered that under certain circumstances the automatic stop of the start/stop-automatic is prohibited. In this case it is not necessary to fill the accumulator tank in addition to the usual standard oil supply control strategy. The additional filling of the accumulator tank according to the method is prevented, while an automatic stop is blocked. The filling and the emptying of the accumulator tank occurs in line of only the usual standard oil supply control strategy. If so, a higher minimum oil pressure and/or a higher minimum level of the accumulator tank can be controlled, so that the predetermined threshold of the oil pressure is already present or reached quickly, when the blocking of the automatic stop is unblocked, while the motor vehicle stands still with zero vehicle speed.

Particularly the predetermined threshold is determined on the basis of the ratio of the fill volume V of the accumulator tank to the maximum fill volume V_(max) of the accumulator tank, wherein 0.75≦V/V_(max)≦0.99, particularly 0.85≦V/V_(max)≦0.95, preferably V/V_(max)=0.90±0.02 is given. It is considered that the oil pressure depends mainly on the hydrostatic pressure inside the accumulator tank. Controlling the oil pressure can be performed by controlling the level of oil inside the accumulator tank.

Preferably the oil pump is electrically operable and adapted to be fed by electrical energy from a generator for providing a braking force to the motor vehicle. When a driver applies the brakes, the braking energy of the motor vehicle can be used for operating the oil pump. Instead of wasting the braking energy, the braking energy can be converted via the generator, which at least partially supports the braking process, into electric energy for operating the oil pump and/or charging the automotive battery. It is not necessary to use a part of the power provided by the combustion engine and/or to use the automotive battery for pumping oil by means of the oil pump.

A controller is also provided according to an embodiment of the invention for carrying out the method as previously described, wherein the controller comprises at least one sensor for detecting a deceleration of the motor vehicle and/or at least one status parameter, which correlates with the manner of the deceleration, a data input for connection to an oil supply controller, a calculation unit for estimating a future oil pressure of the oil supply based on the status parameter and the actual oil supply control strategy, and an activator output connected to an oil pump for filling an accumulator tank of the oil supply, if the estimated future oil pressure is below a predetermined threshold of the oil pressure. The oil supply controller can provide the usual standard oil supply control strategy for the oil supply system. Due to the data input internal variables of the oil supply controller can be used by the controller according to the invention. The sensor for detecting a deceleration can use the vehicle speed as status parameter so that for instance two measured vehicle speed at two different points of time can be compared for detecting, whether a deceleration is present. The activator output can be a switch for turning on or off the oil pump. The activator output is particularly in parallel to the oil supply controller connected to the oil pump, so that the activation of the oil pump based on the control of the oil supply controller and based on the control of the controller according to the invention can be superposed. Since the accumulator tank is filled in advance of a possible automatic stop a sufficient high oil pressure, when the combustion engine is started again, is safeguarded, wherein the period of time for accomplishing the automatic stop is not lengthened. The period of time until the automatic stop is initiated after a stop of the motor vehicle can even be shortened. This leads to a reduction of the fuel consumption and the CO₂-emissions of the combustion engine without dealing with a too low oil pressure at the start of the combustion engine.

The embodiments of the invention further relate to an oil supply system for a combustion engine and/or a transmission system of a motor vehicle particularly with start/stop-automatic, wherein the oil supply system comprises an oil circuit for providing oil to the combustion engine, an oil pump for pumping oil through the oil circuit, an accumulator tank for storing oil and providing an oil pressure, wherein the accumulator tank is connected to the oil pump for filling the accumulator tank, and a controller, which can be designed as previously described, connected to the oil pump for carrying out the method as previously described. Since the accumulator tank is filled in advance of a possible automatic stop a sufficient high oil pressure, when the combustion engine is started again, is safeguarded, wherein the period of time for accomplishing the automatic stop is not lengthened. The period of time until the automatic stop is initiated after a stop of the motor vehicle can even be shortened. This leads to a reduction of the fuel consumption and the CO₂-emissions of the combustion engine without dealing with a too low oil pressure at the start of the combustion engine.

These and other aspects of the invention will be apparent from and elucidated with reference to a preferred embodiment described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction with the following drawing figure where FIG. 1 is a schematic diagram showing a vehicle speed over the time.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description.

As illustrated in FIG. 1 a motor vehicle may comprise a vehicle speed v₁ and can be decelerated at a time t₁. Under the assumption of a constant deceleration the vehicle speed decreases until at a time t₃ a vehicle speed of v₀=0 km/h is reached. Usually it takes a period of time at zero vehicle speed v₀ until a start/stop-automatic of the motor vehicle initiates an automatic stop of a combustion engine of the motor vehicle at a time t₄.

From time t₁ on the method monitors whether a minimum oil pressure for an oil supply system will be provided at the time t₄. When for example the actual time is t₂ it is calculated based on the actual vehicle speed v₂ and the actual amount of the deceleration a={dot over (ν)}₂ a stop-time t_(stop) until time t₄ is reached. A delay time t_(delay)=t₄−t₃ until the start/stop-automatic of the motor vehicle initiates an automatic stop after reaching zero vehicle speed is considered. When the method calculates that the remaining time t_(stop) is only hardly sufficient for reaching the intended minimum oil pressure, when an oil pump is operated at full power, the oil pump is activated for filling an accumulator tank, by means of which the intended oil pressure of the oil supply system can be provided. When the combustion engine stops at time t₄ a sufficient oil pressure is safeguarded for starting the combustion engine without the need of operating the oil pump at the same time.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. 

1. A method for operating an oil supply of a motor vehicle, comprising the steps of: detecting a deceleration of the motor vehicle; monitoring at least one status parameter that correlates with a manner of the deceleration; estimating a future oil pressure of the oil supply based on a status parameter and an actual oil supply control strategy; and activating an oil pump for filling an accumulator tank of the oil supply if an estimated future oil pressure is below a predetermined threshold of an oil pressure.
 2. The method according to claim 1, wherein the status parameter is an amount of the deceleration.
 3. The method according to claim 1, wherein the status parameter is a speed of the motor vehicle.
 4. The method according to claim 1, wherein the status parameter is a brake status.
 5. The method according to claim 1, wherein based on at least one status parameter, a stop-time (t_(stop)) is calculated, until which a speed of the motor vehicle will be zero due to a start/stop-automatic will occur, and the future oil pressure is calculated for an end of the stop-time (t_(stop)).
 6. The method according to claim 1, wherein based on at least one status parameter, a stop-time (t_(stop)) is calculated, until which an automatic stop of a combustion engine due to a start/stop-automatic will occur, and the future oil pressure is calculated for an end of the stop-time (t_(stop)).
 7. The method according to claim 1, wherein the oil pump is activated, if an automatic stop of a start/stop-automatic is unblocked, wherein the automatic stop is particularly blocked when a charge of an automotive battery is below a predetermined value.
 8. The method according to claim 1, wherein the oil pump is activated, if an automatic stop of a start/stop-automatic is unblocked, wherein a value of a vehicle component is out of a predetermined range.
 9. The method according to claim 1, wherein the oil pump is activated, if an automatic stop of a start/stop-automatic is unblocked, wherein a combustion engine control is on override mode from a subsystem particularly from a control.
 10. The method according to claim 1, wherein the predetermined threshold is determined on a basis of a ratio of a fill volume V of the accumulator tank to a maximum fill volume V_(max) of the accumulator tank, wherein 0.75≦V/V_(max)≦0.99.
 11. The method according to claim 1, wherein the predetermined threshold is determined on a basis of a ratio of a fill volume V of the accumulator tank to a maximum fill volume V_(max) of the accumulator tank, wherein 0.85≦V/V_(max)≦0.95.
 12. The method according to claim 1, wherein the predetermined threshold is determined on a basis of a ratio of a fill volume V of the accumulator tank to a maximum fill volume V_(max) of the accumulator tank, wherein V/V_(max)=0.90±0.02 is given.
 13. The method according to claim 1 wherein the oil pump is electrically operable and adapted to be fed by electrical energy from a generator for providing a braking force to the motor vehicle.
 14. A apparatus adapted to operate an oil supply of a motor vehicle, comprising: a sensor adapted to detect a status parameter that correlates with a manner of a deceleration; a data input adapted to connect to an oil supply controller; a calculation unit adapted to estimate a future oil pressure of the oil supply based on the status parameter and an actual oil supply control strategy; and an activator output connected to an oil pump for filling an accumulator tank of the oil supply, if an estimated future oil pressure is below a predetermined threshold of an oil pressure.
 15. The apparatus according to claim 14, wherein the status parameter is an amount of the deceleration.
 16. The apparatus according to claim 14, wherein the status parameter is a speed of the motor vehicle.
 17. The apparatus according to claim 14, wherein the status parameter is a brake status.
 18. The apparatus according to claim 14, wherein based on at least one status parameter, a stop-time (t_(stop)) is calculated, until which a speed of the motor vehicle will be zero due to a start/stop-automatic will occur, and the future oil pressure is calculated for an end of the stop-time (t_(stop)).
 19. The apparatus according to claim 14, wherein based on at least one status parameter, a stop-time (t_(stop)) is calculated, until which an automatic stop of a combustion engine due to a start/stop-automatic will occur, and the future oil pressure is calculated for an end of the stop-time (t_(stop)).
 20. The apparatus according to claim 14, wherein the oil pump is activated, if an automatic stop of a start/stop-automatic is unblocked, wherein the automatic stop is particularly blocked when a charge of an automotive battery is below a predetermined value. 